Long-range correlations of soil water content time series under tillage and different cover crops in a semiarid vineyard.

Résumé

We explored the suitability of multifractal detrended fluctuation analysis(MFDFA) to characterize the temporal dynamics of soil water content (SWC),we analysed the origin of the multifractality of time series of the dynamic ofSWC and we investigated how this dynamic was affected by different soil treat-ments and depths, through the characterization of long-range correlations.Temporal data of SWC from conventional tillage and two different cover cropsat three different depths in a Mediterranean vineyard were examined. Thedataset spanned 18 months in 30-min intervals. We investigated if SWCdynamics, as reflected by long-range dependencies, can be detected and quan-tified by MFDFA in the form of scaling laws. We analysed the randomly shuf-fled series associated with temporal data of SWC to investigate if the detectedmultifractality of the data reflected either a broad density function of thevalues of the series or different long-range correlations for small and large fluc-tuations in the dataset. Finally, the impact of treatment and depth on the vari-ation of long-range dependencies was studied. Our results suggest that thetime records of soil moisture in a Mediterranean vineyard show a multifractalbehaviour compatible with complex patterns of long-range correlations. More-over, this complex structure is affected by depth, as depicted by the statisticallysignificant variation of the generalized Hurst exponent h(0), which controlsthe logarithmic mean of the fluctuation of SWC over a period of time. No sig-nificant interactions between treatments and depth was found. This suggeststhat soil properties that influence soil water dynamics at each depth are notaffected by cover crop treatments. This could be due to the fact that the experi-ment lasted less than 2 years and no long-term interactions were present atthis time interval.Highlights• Multifractal detrended fluctuation analysis (MFDFA) characterizes soilwater content dynamics.• MFDFA detects the influence of soil depth on long-range correlations.• Time series of soil moisture are multifractals compatible with complex pat-terns of long-range correlations.• Long-range dependencies are affected by depth but no interaction has beenfound between soil treatment and depth.